The present invention is in the field of crystallisation, more particularly, in the field of crystallisation as a means of separating and purifying chemical substances.
The selective crystallisation of a desired substance from a mixture of substances by emulsion crystallisation is known. In emulsion crystallisation processes, the desired substance is selectively crystallised by forming emulsified droplets of the mixture and then adding a suspension of seed crystals of the desired substance to the emulsion to thereby selectively crystallise that substance, or by cooling the emulsion to induce crystallisation (c.f. EP 0 548 028 A1; Davey et al., Nature, Vol. 375, pp. 664-666 (Jun. 22, 1995); I. Holxc3xa9ci, Chemicky prûmysi 14/39, pp. 638-641 (1964)).
It has now been surprisingly found that the yield of purified component can be dramatically increased by seeding with seed crystals of the desired substance and one or more other substances in the emulsion. The other substance(s) are chosen according to the concentration at which they are present in the mixture and according to their physico-chemical characteristics to allow their selective crystallisation and their subsequent removal, as will be described in detail below. By way of the process of the present invention, yields can be dramatically increased. This improvement represents an important advantage in commercial separation processes.
The present invention provides a crystallisation process for separating a desired substance from an aggregate mixture in which process an emulsion of droplets in a continuous phase containing the aggregate mixture is formed and supersaturated. Supersaturation is achieved by techniques known in the art, such as by disolving an excess amount of aggregate mixture in the emulsion by means of ultrasound or employing elevated temperatures. This process is characterised in that the emulsion is seeded with seed crystals of the desired substance and seed crystals of at least one other substance in the aggregate mixture to effect crystallisation of the desired substance and the other substance(s) in the continuous phase. The present invention also encompasses substances separated by the inventive process, and devices for carrying out the process, as are described hereinafter.